Decontamination methods are used in a broad range of applications, and have used an equally broad range of decontaminating agents. As used herein the term “decontamination” refers to the inactivation of bio-contamination, and includes, but is not limited to, sterilization and disinfection.
Gaseous and vaporous decontamination systems rely on maintaining certain process parameters in order to achieve a target decontamination assurance level. For hydrogen peroxide vapor decontamination systems, those process parameters include the concentration of the hydrogen peroxide vapor, the degree of saturation, the temperature and pressure, and the exposure time. By controlling these process parameters, the desired decontamination assurance levels can be successfully obtained while avoiding condensation of the hydrogen peroxide due to vapor saturation.
Conventional vaporized hydrogen peroxide (VHP) decontamination systems for decontaminating enclosures (such as rooms or isolators), are generally closed-loop systems that contain a destroyer and a dryer within the system. In such closed-loop systems, a decontaminant is continuously conveyed through the enclosure. Decontaminant exiting the enclosure is directed to the destroyer to break down the vaporized hydrogen peroxide into water and oxygen. This type of arrangement allows the vaporized hydrogen peroxide concentration within the system to be maintained at a desired concentration depending on the airflow and decontaminant (typically 35% hydrogen peroxide, 65% water, by weight in a liquid state).
A conventional VHP decontamination system for decontaminating an enclosure has a decontamination cycle comprised of four (4) basic operating phases, namely, (1) a dehumidification phase, (2) a conditioning phase, (3) a decontamination phase, and (4) an aeration phase. In the dehumidification phase the relative humidity within the enclosure is reduced by using a dryer. After the dehumidification phase is complete, the conditioning phase commences, wherein vaporized hydrogen peroxide is injected into the enclosure at a relatively high rate to bring the hydrogen peroxide concentration up to a desired level in a short period of time. After the conditioning phase, the decontamination phase is run where the injection rate may be modified to maintain the hydrogen peroxide vapor in the enclosure at a constant concentration level. In the aeration phase that follows the decontamination phase, the enclosure is aerated by stopping injection of the hydrogen peroxide vapor, and removing hydrogen peroxide vapor from the enclosure. A destroyer may be used to break down the hydrogen peroxide vapor into water and oxygen. Aeration continues until the concentration of hydrogen peroxide in the enclosure is below a threshold concentration level (e.g., 1 ppm).
Existing closed-loop VHP decontamination systems have a system airflow that is limited by the capacity of the dryer used therein. In this respect, if the airflow exceeds the dryer capacity, the air circulated therethrough is inadequately dehumidified. Where the VHP decontamination system is being used with a large enclosure, the limited dryer capacity can be particularly disadvantageous.
Some dryers have their own internal blowers that are continuously operated at full speed in order to quickly dehumidify a maximum volume of air. However, where the dryer having its own internal blower is a high capacity dryer, the airflow provided by the internal blowers may exceed the airflow rate suitable for certain operating phases of a VHP decontamination system (e.g., decontamination phase).
The present invention overcomes the foregoing problems, along with others, by providing a VHP decontamination system including an air bypass that allows efficient utilization of a high capacity dryer having a continuously operating internal blower.